A New Zealand company is still hopeful about getting the Moon Express into high Earth orbit by the year's end, but the task depends upon, as yet, unproven technology working.

A private company planning a Moon mission involving New Zealand's Rocket Lab says it still hopes to reach the lunar surface by as early as the end of the year.

Florida-based Moon Express signed a deal with Rocket Lab in 2015 and if it can reach the Moon by the end of the year and accomplish a number of tasks it could win US$20 million ($26m).

Its robotic lander would be blasted into orbit aboard Rocket Lab's Electron rocket.

The MX-1 lunar lander is reportedly about 1.8m tall, weighs about 250kg and would fly to the moon over about four days after being delivered into high Earth orbit by the Electron.

The US$20 million Google Lunar XPRIZE will go to the first private operation to place a spacecraft on the Moon's surface, travel 500m and transmit high-definition video and images back to Earth.

Rocket Lab says it is still the plan to get Moon Express into orbit by the end of the year. However, that will depend on as yet unproven technology to work.

Rocket Lab is in the early stages of a three-vehicle test programme and Moon Express is still developing its lander at its facilities at Cape Canaveral, from where Apollo missions were launched.

Rocket Lab's first test launch successfully made it to space in late May. The first stage performed as it should but the second stage failed to deliver the payload to orbit.

Results of data analysis from the test flight could be available some time next week.

Earlier this month Rocket Lab founder Peter Beck said the company and its investors had confidence in the programme and they had another five rockets in various stages of production.

Beck said then a second test launch was about two or three months away and the company hoped to get its commercial launches underway as soon as it was satisfied with the test programme.

Moon Express unveiled design details for its lunar spacecraft at a hearing held by the House Science, Space and Technology Committee last week.

It said it was planning three missions to the moon by the end of 2020, with the ultimate goal of establishing a permanent station near the moon's south pole and returning lunar dust and rock samples to Earth for analysis of minerals.

The company says the initial Lunar Scout expedition - as early as this year - will be the first commercial voyage to the Moon.

"This historic expedition will demonstrate the cost-effectiveness of entrepreneurial approaches to space exploration, carrying a diverse manifest of payloads including the International Lunar Observatory," it said.

"Our goal is to open the lunar frontier for all of us, ultimately expanding Earth's economic and social spheres to our eighth continent, the Moon."

The company was awarded US$1 million by Google earlier this year as the only team to flight test a prototype of its lander.

In 2015 Rocket Lab and Moon Express signed a deal for three launches aboard the Electron.